5891 Please help us to identify the insect who left these cocoons in our books. We found about 15 hard dark brown cocoons 2cm long attached to opposite side of the books in a bookshelf. Inside them there are light yellow larvae. Now when we found them it’s the end of august. We live in Ukraine. Thank you very much for your help.
These are ‘nests’ of a mud dauber wasp (Hymenoptera: Sphecidae), likely in the genus Sceliphron. The adult wasps place live but paralyzed spiders within these structures that their larvae then feed upon. See http://tinyurl.com/h7pqegu for images and more information. Ed Saugstad, retired entomologist; Sinks Grove, WV.